pyln: Plugin methods and hooks refuse to set results twice #4094
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We had a couple of instances where a plugin would be killed by
lightningd
because we were returning a result of an exception twice, and it was hard to
trace down the logic error in the user plugin that caused that. This patch
adds a traceback the first time we return a result/exception, and raise an
exception with a stacktrace of the first termination when a second one comes
in.
This can still terminate the plugin, but the programmer gets a clear
indication where the result was set, and can potentially even recover from it.
Changelog-Added: pyln: Plugin method and hook requests prevent the plugin developer from accidentally setting the result multiple times, and will raise an exception detailing where the result was first set.